This invention relates to a spring-type operating mechanism for a circuit interrupter in which the rotational force of an electric motor charges a spring and the charged spring energy is used to close and open the circuit interrupter, and particularly to the improvements thereof.
One example of a conventional spring-type operating mechanism for a circuit interrupter, which has the structure shown in FIGS. 1 to 3, will be explained. In FIG. 2, a lever 3 is rotatably mounted on a pin 2 supported by a frame 1, and a pin 4 on one end of the lever 3 is connected to an unillustrated interrupting unit and is biased in the direction of an arrow C by means of an unillustrated opening spring. A groove 5 is formed in the other end of the lever 3 and a roller 6 is rotatably mounted within the groove 5 on a pin 7. Also, a pin 8 is rotatably supported by the lever 3 within the groove 5 so that it engages a latch 10 rotatably supported by the frame 1 through a pin 9 to prevent the lever 3 from rotating counterclockwise in the figure in the direction of the arrow C about the pin 2 due to the biasing force. While the latch 10 is urged to rotate clockwise in the figure about the pin 9 due to a force from the pin 8, the latch 10 is prevented from doing so by contact with a trigger 12 rotatably mounted on the frame 1 through a pin 11. The latch 10 and the trigger 12, are provided with return springs 13 and 14, respectively. The end of the trigger 12 opposite from the end which engages the latch 10 abuts against a plunger 15 which moves to the right in FIG. 2 when a tripping electromagnet 16 is energized. The frame 1 also rotatably supports a main shaft 17 on which a cam 18 is secured.
As shown in FIG. 3, a ratchet wheel 19 is fixed on the main shaft 17 and has a groove 20 formed in its entire outer circumference, and teeth 21 are provided on both sides of the groove 20 over about a half of the circumference as shown in FIG. 1. While the ratchet wheel 19 is urged to rotate in the counterclockwise direction as viewed in FIG. 3 by a closing spring 37 which will be explained later, its rotation is prevented by the engagement of a pin 22 rotatably mounted on the ratchet wheel 19 with a latch 24 rotatably mounted on the frame 1 by a pin 23. While the latch 24 is urged to rotate counterclockwise as viewed in FIG. 3 by the force applied to it through the pin 22, its rotation is prevented by engagement with a trigger 26 rotatably mounted on the frame 1 by a pin 25. The latch 24 and the trigger 26 are provided with return springs 27 and 28. The trigger 26 is adapted to abut against the end of a plunger 29 which moves to the right in FIG. 3 when the closing electromagnet 30 is energized. The frame 1 also rotatably supports an eccentric shaft 31 in the vicinity of the ratchet wheel 19. The eccentric shaft 31 is connected to an unillustrated electric motor. The eccentric shaft 31 has formed thereon two eccentric portions on which a smaller pawl 32 and a larger pawl 33 are rotatably mounted. The smaller and the larger pawls 32 and 33 engage the teeth 21 of the ratchet wheel 19 and rock as the eccentric shaft 31 rotates to cause the counterclockwise rotation of the ratchet wheel 19. One end of a spring rod 34 is rotatably mounted on the ratchet wheel 19 through a pin 35 and the other end of the spring rod 34 engages the spring holder 36. The spring holder 36 contacts one end of a closing spring 37 disposed within a spring guide 38 to receive the spring force in the state shown in the figure. This spring force is transmitted to the main shaft 17 to rotate it counterclockwise.
The operation of the above-described apparatus will now be described, with an interrupting operation being first explained. In FIG. 2, when the tripping electromagnet 16 is excited, the plunger 15 moves to the right in the figure and pushes the trigger 12, rotating it clockwise, thereby disengaging the trigger 12. Then the latch 10 rotates clockwise and disengages from the pin 8. The lever 3 is then rotated counterclockwise by the spring force in the direction of the arrow C and opens the unillustrated interrupting unit connected to the pin 4. In this case, since the main shaft 17 does not rotate, the portion illustrated in FIG. 3 is not operated and remains in the illustrated position during the interruption. FIG. 4 shows the state of the parts shown in FIG. 2 after the completion of the interrupting operation.
Next, the closing operation will be described. Referring to FIGS. 3 and 4, when the closing electromagnet 30 is excited, the plunger 29 moves to the right in FIG. 3 and abuts against the trigger 26, causing it to rotate in the clockwise direction, so that the engagement between the trigger 26 and the latch 24 is released and the latch 24 is rotated counterclockwise to disengage from the pin 22. This causes the ratchet wheel 20 together with the main shaft 17 to be rotated counterclockwise by the spring force of the closing spring 37. The rotation of the main shaft 17 causes the cam 18 to rotate counterclockwise, and as the cam 18 rotates counterclockwise from the position shown in the figure, the roller 6 rolls on the cam surface of the cam 18 and rotates the lever 3 clockwise, whereby the unillustrated interrupting unit connected to the pin 4 is closed and the unillustrated trip spring is charged. When the lever 3 is rotated clockwise to the position shown in FIG. 5, the latch 10 and the trigger 12 return due to the return springs 13 and 14, and the latch 10 engages the pin 8, so that even if the cam 18 rotates further and the roller 6 is separated from the cam surface, the rotation of the lever 3 in the counterclockwise direction due to the spring force in the direction of the arrow C of the trip spring is prevented and the closed position is maintained.
On the other hand, the main shaft 17 is rotated counterclockwise by the spring force of the closing spring 37 applied through the spring holder 36, the spring rod 34, and the ratchet wheel 19 until it reaches the lower dead point which is the most expanded state of the closing spring 37, and the main shaft 17 further rotates due to the rotational energy in the main shaft 17, the cam 18 and the ratchet wheel 19 provided by the closing spring 37 while charging the closing spring 37, and after pausing for a while, the main shaft 17 commences to be rotated clockwise by the closing spring force until it is stopped by the engagement of the teeth 21 of the ratchet wheel 19 with the tips of the smaller pawl 32 and the larger pawl 33.
FIG. 5 illustrates the state of the portion shown in FIG. 4 after the closing operation has been completed, and FIG. 6 illustrates the state of the portion shown in FIG. 3.
Next, the closing spring charging operation will be described. When the eccentric shaft 31 is rotated by the unillustrated electric motor from the state shown in FIG. 6 in which the tips of the smaller pawl 32 and the larger pawl 33 engage the teeth 21 of the ratchet wheel 19, rocking motions effected in the tips of the smaller pawl 32 and the larger pawl 33 push the teeth 21 to rotate the ratchet wheel 19 counterclockwise. As the ratchet wheel 19 rotates the main shaft 17 rotates and the closing spring 37 is charged. When the ratchet wheel 19 is rotated close to the position shown in FIG. 3, the latch 24 and the trigger 26 are returned to their original position due to the return springs 27 and 28, and when the ratchet wheel 19 is rotated counterclockwise beyond the state in which the spring is most compressed by the closing spring 37, the pin 22 on the ratchet wheel 19 engages the latch 24 to maintain the charged condition of the closing spring previously described and shown in FIG. 3.
In such a conventional spring-type operating mechanism, at the last moment of the closing operation in which the teeth 21 of the ratchet wheel 19 engage with the smaller and the larger pawls 32 and 33, these pawls are subjected to impacts of excessive torque due to the closing spring 37. Therefore, the teeth 21 of the ratchet wheel 19 and the tips of the smaller pawl 32 and the larger pawl 33 may be damaged in such a manner that the charging of the closing spring cannot be effected.